Encapsulation of propionic acid within the aqueous phase of water-in-oil emulsions: reduced thermal volatilization and enhanced gastrointestinal stability.

Propionic acid (PA) is a water-soluble substance that has been shown to be beneficial for improving colon-related diseases. However, its appliance as a nutraceutical ingredient is hampered by its volatility, irritating odor, and easy absorption in the stomach and small intestine. A chitosan solution containing propionic acid was dispersed in a palm oil/corn oil mixture with polyglycerol polyricinoleate (PGPR) to form PA-loaded water-in-oil (W/O) emulsions. The stability of the emulsions was improved by the inclusion of both chitosan and palm oil, where the chitosan reduced the emulsion particle size and palm oil increased the viscosity. The thermal volatility and storage stability of the encapsulated propionic acid were significantly improved due to the stability of emulsion structure and hydrogen bonding between chitosan and propionic acid. Around 56% of propionic acid remained within the aqueous phase after the simulated gastrointestinal digestion. Our results indicate that W/O emulsions might be candidates as colon-targeted delivery systems for propionic acid, which could be beneficial for maintaining colon health.

Enhancing the oxidative stability of algal oil emulsions by adding sweet orange oil: Effect of essential oil concentration.

The effects of sweet orange essential oil (SOEO) concentration (0-12.5% of oil phase) on the physical stability, oxidative stability, and interfacial composition of algal oil-in-water emulsions containing sodium caseinate-coated oil droplets was examined. SOEO addition had no influence on the microstructure and physical stability of the algal oil emulsions. The addition of SOEO enhanced the oxidation stability of algal oil emulsion. As an example, the values of algal oil emulsions with 0 and 10% SOEO were 198 and 100 mmol/kg algal oil after 16 days of accelerated oxidation, respectively. The absorbed protein level was higher in the algal oil emulsion containing 10% SOEO (70%) than in 0% SOEO (57%). This result suggested that the presence of SOEO enhanced the interfacial thickness, possibly by interacting with the casein molecules. A thicker protein layer may have helped to retard the oxidation of the omega-3 oils inside lipid droplets.

Rheological and microstructural properties of cold-set emulsion gels fabricated from mixed proteins: Whey protein and lactoferrin.

Cold-set emulsion gels were fabricated from oil droplets coated by mixed proteins: whey protein and lactoferrin. The impact of protein composition, droplet concentration, pH, and ionic strength on the microstructure, texture, and stability of the cold-set emulsion gels was determined. Protein composition had a major influence on gel strength, with the strongest emulsion gels being formed at an optimized protein composition (0.5 wt% whey protein and 1.5 wt% lactoferrin). The storage modulus of the emulsion gels increased from 149 to 1590 Pa as the droplet concentration increased from 10 to 40 wt%. The gel strength could also be modulated by adjusting pH, with the strongest gels being formed at pH = 6.5, where the net charge on the droplets was neutral. Increasing the ionic strength weakened the electrostatic interactions, which inhibited droplet aggregation and led to a decrease in gel strength. These results may be useful for designing cold-set emulsion gels with rheological properties that can be tailored for specific commercial products.

Enhancement of the solubility, stability and bioaccessibility of quercetin using protein-based excipient emulsions.

Emulsion-based excipient foods were developed to improve the bioaccessibility of an important hydrophobic nutraceutical: quercetin. Protein-stabilized oil-in-water excipient emulsions were prepared using sodium caseinate, whey protein isolate, or soy protein isolate as an emulsifier. These emulsions were then mixed with powdered quercetin and heated to simulate a cooking process. The excipient emulsions had relatively small droplet sizes (d < 270 nm) and remained stable against coalescence after exposure to boiling (100 °C for 60 min). In particular, casein was shown to be better at adsorbing to oil-water interface and contributed to a more stable interfacial layer than the other two proteins. Quercetin was solubilized in the emulsions during heating, which may be attributed to dissolution in the oil phase and complexation with proteins. There were appreciable differences in quercetin bioaccessibility in excipient emulsions stabilized by different emulsifiers (≈74% for casein, 54% for whey protein, 22% for soy protein, and 58% for Tween). This study suggests that milk proteins may be natural alternatives to synthetic surfactants for forming stable excipient emulsions capable of enhancing nutraceutical bioaccessibility.

Gastrointestinal Fate of Fluid and Gelled Nutraceutical Emulsions: Impact on Proteolysis, Lipolysis, and Quercetin Bioaccessibility.

Fluid and gelled nutraceutical emulsions were formulated from quercetin-loaded caseinate-stabilized emulsions by the addition of gellan gum with or without acidification with glucono-δ-lactone. Gellan gum addition increased the viscosity or gel strength of the fluid and gelled emulsions, respectively. The behavior of the nutraceutical emulsions in a simulated gastrointestinal tract depended upon their initial composition. Fluid emulsions containing different gellan gum levels (0-0.2%) had similar protein and lipid hydrolysis rates as well as similar quercetin bioaccessibility (∼51%). Conversely, proteolysis, lipolysis, and quercetin bioaccessibility decreased with an increasing gellan gum level in the gelled emulsions. In comparison to gelled emulsions, fluid emulsions were digested more rapidly and led to higher quercetin bioaccessibility. There was a good correlation between quercetin bioaccessibility and the lipolysis rate. These findings are useful for designing nutraceutical-loaded emulsions that can be used in a wide range of food products with different rheological properties.